Short sight

Short sight (myopia) makes far things blurry, usually because the eyeball has grown a little too long. It often starts in childhood and is becoming much more common. Fair tests in schools show that time outdoors, even in shade, helps stop it from starting; there is much less evidence that it slows short sight once it has begun. The evidence about screens and close-up work is mixed. Glasses fix the blur.

Watch · Depth 1 · 64 sForty minutes outsideSara squints at the board and her parents blame her phone. What short sight is, why it is becoming so common, the school trials that found time outdoors helps stop it starting, and what is known about screens.